Renderer process can allocate anonymous shared memory without help from browser process on Windows.

chrome/renderer/print_web_view_helper.cc

Index: chrome/renderer/print_web_view_helper.cc
===================================================================
--- chrome/renderer/print_web_view_helper.cc	(revision 172434)
+++ chrome/renderer/print_web_view_helper.cc	(working copy)
@@ -1398,14 +1398,15 @@
     printing::Metafile* metafile,
     base::SharedMemoryHandle* shared_mem_handle) {
   uint32 buf_size = metafile->GetDataSize();
-  base::SharedMemoryHandle mem_handle =
-      content::RenderThread::Get()->HostAllocateSharedMemoryBuffer(buf_size);
-  if (base::SharedMemory::IsHandleValid(mem_handle)) {
-    base::SharedMemory shared_buf(mem_handle, false);
-    if (shared_buf.Map(buf_size)) {
-      metafile->GetData(shared_buf.memory(), buf_size);
-      shared_buf.GiveToProcess(base::GetCurrentProcessHandle(),
-                               shared_mem_handle);
+  scoped_ptr<base::SharedMemory> shared_buf(
+      content::RenderThread::Get()->HostAllocateSharedMemoryBuffer(
+          buf_size).release());
+
+  if (shared_buf.get()) {
+    if (shared_buf->Map(buf_size)) {
+      metafile->GetData(shared_buf->memory(), buf_size);
+      shared_buf->GiveToProcess(base::GetCurrentProcessHandle(),
+                                shared_mem_handle);
       return true;
     }
   }